[FFmpeg-devel] [PATCH 1/2] avfilter/vf_perspective: factor the interpolation code out so that it's usable by other filters

[Michael Niedermayer]

On Thu, Jun 12, 2025 at 11:38:59AM +0200, Quentin RENARD wrote:
> As mentioned here (https://ffmpeg.org/pipermail/ffmpeg-devel/2025-June/344593.html), this is the first step of a 2 steps patch: move the interpolation code out of the vf_perspective filter so that we can use it in a new zoompan filter and apply scale/crop floating point precision there.
> 
> Signed-off-by: Quentin Renard <contact-github at asticode.com>
> ---
>  libavfilter/Makefile         |   2 +-
>  libavfilter/perspective.c    | 404 +++++++++++++++++++++++++++++++++++
>  libavfilter/perspective.h    |  67 ++++++
>  libavfilter/vf_perspective.c | 372 +++-----------------------------
>  4 files changed, 497 insertions(+), 348 deletions(-)
>  create mode 100644 libavfilter/perspective.c
>  create mode 100644 libavfilter/perspective.h
> 
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index 97f8f17272..7c6dfcf4bf 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -426,7 +426,7 @@ OBJS-$(CONFIG_PAD_OPENCL_FILTER)             += vf_pad_opencl.o opencl.o opencl/
>  OBJS-$(CONFIG_PALETTEGEN_FILTER)             += vf_palettegen.o palette.o
>  OBJS-$(CONFIG_PALETTEUSE_FILTER)             += vf_paletteuse.o framesync.o palette.o
>  OBJS-$(CONFIG_PERMS_FILTER)                  += f_perms.o
> -OBJS-$(CONFIG_PERSPECTIVE_FILTER)            += vf_perspective.o
> +OBJS-$(CONFIG_PERSPECTIVE_FILTER)            += vf_perspective.o perspective.o
>  OBJS-$(CONFIG_PHASE_FILTER)                  += vf_phase.o
>  OBJS-$(CONFIG_PHOTOSENSITIVITY_FILTER)       += vf_photosensitivity.o
>  OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
> diff --git a/libavfilter/perspective.c b/libavfilter/perspective.c
> new file mode 100644
> index 0000000000..ab200f8532
> --- /dev/null
> +++ b/libavfilter/perspective.c
[...]
> +static int perspective_resample_cubic(AVFilterContext *ctx, void *arg,
> +                          int job, int nb_jobs)
> +{
[...]
> +static int perspective_resample_linear(AVFilterContext *ctx, void *arg,
> +                           int job, int nb_jobs)
> +{
[...]
> +static int calc_luts(PerspectiveResampleContext *s, int w, int h, double ref[4][2])
> +{
[...]
> diff --git a/libavfilter/vf_perspective.c b/libavfilter/vf_perspective.c
> index 58510f6f13..f5766eed7a 100644
> --- a/libavfilter/vf_perspective.c
> +++ b/libavfilter/vf_perspective.c
[...]
> -static int calc_persp_luts(AVFilterContext *ctx, AVFilterLink *inlink)
[...]
> -static int resample_cubic(AVFilterContext *ctx, void *arg,
> -                          int job, int nb_jobs)
> -{
[...]
> -static int resample_linear(AVFilterContext *ctx, void *arg,
> -                           int job, int nb_jobs)
> -{

please keep the functions in the same order so that a diff between
new libavfilter/perspective.c
and
old libavfilter/vf_perspective.c

is easy readable

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Old school: Use the lowest level language in which you can solve the problem
            conveniently.
New school: Use the highest level language in which the latest supercomputer
            can solve the problem without the user falling asleep waiting.
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